The in vitro anamnestic antibody response of rabbit lymph node cells to keyhole limpet hemocyanin is sharply regulated by the concentration of added antigen. This response is greatly enhanced when cholera enterotoxin or dibutyrl cyclic AMP is added to the se cultures with antigen. The objectives of the proposed research are as follows: 1. To examine conditions for consistent regulation of the in vitro and in vivo antibody responses to hemocyanin and other antigens by agents like cholera toxin that presumably modify cellular cAMP and/or cGMP pathways. 2. To determine the effects of antigen or antigen agents like cholera toxin on T and/or B lymphocytic structures (receptors) and functions of the cell membrane like capping response to mitogens, uptake of amino acids, antibody synthesis and release. 3. To correlate, if possible, the regulation of the antibody response by antigen, cholera toxin alone, or a combination of agents with consistent changes in cAMP or cGMP levels or in activities of adenylate cyclase, guanylate cyclase, or phosphodiesterase.